Presser mechanism for sewing machines



Feb; 10, 1970 R. E. JOHNSON PRESSER MECHANISM FOR SEWING MACHINES 'Filed June 28, 1968 l N VENTORI. /Ralph E. Johnsafl WITNESS United States Patent 3,494,314 PRESSER MECHANISM FOR SEWING MACHINES Ralph E. Johnson, Boonton, N.J., assignor to The Singer Company, New York, N.Y., a corporation of New Jersey Filed June 28, 1968, Ser. No. 740,891 Int. Cl. D05b 29/00 US. Cl. 112238 6 Claims ABSTRACT OF THE DISCLOSURE A sewing machine formed with a frame including a work supporting bed and a bracket arm terminating in a head and overhanging the bed and including a substantially vertical presser bar mounted in the head for endwise sliding movements. A torsion rod is mounted on the sewing machine frame and is connected to the presser bar so that the torque exerted by the torsion rod is applied to bias the presser bar downwardly.

Background of the invention In the prior art coil springs and leaf springs have been used in various arrangements to apply a downward force or bias on the presser bar to hold the presser foot down against the cloth material being sewn and thereby sandwich the material between the bottom of the presser foot and the opposing feed dog. In one such known arrangement a coil spring is mounted in the head of a machine and an adjustment mechanism therefor is mounted on the exterior of the head. The coil spring in such mechanism is relatively bulky, occupies much needed space in the head of the machine and the adjustment mechanism tends to interfere with the operators view of the working area of the machine bed. In the above and other such arrangements that utilize a coil spring, vibrations are set up by the repeated hammering of the feed dog as it raises and lowers in the normal course of its operation. The vibrations thus set up often cause erratic contact of the presser foot with the cloth work material and with varying degrees of pressure when it does contact the cloth, resulting in unreliable cloth feed. In other arrangements the coil spring is mounted above or around the presser bar so that the presser 'bar when it raises must push against the entire mass of the spring, resulting in an increased load on the feed dog. In still further presser mechanisms a leaf spring is utilized to apply a downward pressure on the presser bar, however, the leaf springs also give rise to a harmonic problem, i.e., standing waves are produced in the leaf spring which result in erratic pressure application by the presser foot.

Summary of the invention The present invention comprises a sewing machine having a frame including a work supporting bed, and a feed dog mounted in the bed, a presser bar mounted in the frame for endwise movements and means for applying a pressure on the presser foot to urge the presser foot toward the feed dog. The pressure applying means includes a torsion rod mounted on the frame to which torsion rod a torque is applied and means for applying the torque to urge the torsion rod toward the feed dog.

The present invention avoids the drawbacks existing in prior art mechanisms by providing pressure applying mechanism which occupies very little space in the head of the sewing machine, and in addition permits the location of the torque adjusting device at more convenient positions removed from the vicinity of the work area. Furthermore, the pressure applying torsion rod utilized in the present invention may be tucked away in any number of convenient out of the way or unused areas of the bracket 3,494,314 Patented Feb. 10, 1970 arm in addition to the location shown in the herein disclosed embodiment.

The torsion rod of the present invention has a natural frequency sufiiciently high to avoid the standing waves that occur in the coil and leaf spring arrangements of the prior art, in which coil and leaf spring arrangements the natural frequency is within the frequency range of the reciprocation of the presser 'bar produced by the regular jolts given to the presser foot by the feed dog as the feed dog moves through its cycle. In addition, in comparison with the coil spring and even the leaf spring there is less mass in motion in the torsion rod, reducing the mass which the feed dog must move as it moves up into contact with the presser foot.

It is an object of the present invention to provide an improved presser mechanism for sewing machines.

It is another object of the present invention to provide improved mechanism for applying a pressure or bias to sewing machine presser bars.

It is still another object of the present invention to provide improved mechanism which utilizes a torsion rod to which torque has been applied for applying a pressure or bias to sewing machine presser bars.

Having in mind the above and other objects that will be evident from an understanding of this disclosure, the invention comprises the devices, combinations and arrangements of parts as illustrated in the presently preferred embodiment of the invention which is hereinafter set forth in such detail as to enable those skilled in the art readily to understand the function, operation, construction and advantages of it when read in conjunction with the accompanying drawings.

Brief description of the drawings FIG. 1 is an end view in elevation of a sewing machine incorporating the presser bar pressure applying means of the present invention.

FIG. 2 is a perspective view of the pressure applying means of the present invention with the sewing machine of FIG. 1 illustrated in outline form.

Description of the preferred embodiment In the drawings there is illustrated a sewing machine 10 having a bed 12 from which rises a standard 14 that supports a bracket arm 16 formed at one end with a head 18 in which is mounted a needle bar 20 and a presser bar 22. Secured on the presser bar and needle bar are a presser foot 24 and a needle 26, respectively, which overlie feeding mechanism including a feed dog 28 mounted in the bed 12 and driven through the usual four motion cycle. The stitch forming instrumentalities described are driven in a known manner by mechanism not shown in the drawings.

The presser bar 22 is mounted for endwise sliding movement in the head 18 and has secured to the top segment thereof a collar 30. The collar 30 and that segment of the presser bar 22 surrounded by the collar is shown extending above the head 18 but may be enclosed within the confines of the sewing machine should the machine design so provide. Secured to the bottom of the collar 30 by any suitable means such as welding is a substantially U-shaped connecting bracket 32. The bracket 32 is formed with parallel upper and lower legs 34 and 36, respectively, which in turn are substantially parallel with the bed 12 of the sewing machine. The legs 34 and 36 are connected by a vertical leg 37 which depends through an opening 38 formed in the top of the head 18. The free end segment 40 of the upper leg 34 is formed with an opening which receives the presser bar 22 and is also formed with an ear 42 which ear extends parallel with the leg 34 outwardly away from the end face 44 of the head 18 to overhang the bed 12. Beneath the ear 42 on the end face 44 is pivotally mounted a lifting lever 4-6 formed with a handle 48, a lifting arm 50, and a cam face 51 for elevating the presser rod. The lever 46 is so positioned that when the handle 48 is moved away from the operator the lifting arm 50 is brought into contact with the underside of the ear 42 thereby to apply an upward force on the U-shaped bracket 32.

Mounted on the side 52 of the bracket arm 16 facing the operator is a torsion rod 54 parallel with the bed 12 and the side 52. In the illustrated version the torsion rod 54 is cylindrical in cross section and extends from the standard 14 to and through the head 18 and a short distance beyond. The end of the torsion rod 54 terminating at the standard is integrally connected to an adjusting lever arm 56 that depends from the torsion rod 54 at right angles thereto. The other end extremity of the rod 54 passes through a hole 57 in the head 18 and is integrally connected at its very end to a connecting lever arm 58 which extends at right angles to the torsion rod in a direction toward the operator and substantially parallel with the bed 12. The free end segment of the lever arm 58 forms a finger 60 that is turned inwardly toward the head 18 to lie upon the upper surface of the lower leg 36 of the U-shaped bracket 32. It is noted that the lever arm 56 while it is at right angles to the torsion rod 54 does not in its untensioned state extend vertically relatively to the horizontal surface of the bed 12. Rather, the adjusting lever arm 56 must extend, in its untensioned state, at an angle of less than 90 from a plane taken through the finger 60 and the torsion rod 54, thereby bringing the lever arm 56 away from the face of the standard 14. This provides an angle through which the lever arm may be moved to develop a torque in the torsion rod 54.

The torsion rod 54 is held against vertical movement by two horizontally spaced and vertically aligned brackets 62 which are secured to the side 52 of the bracket arm 16 and act as bearings, along with the surfaces defining the hole 57, for the torsion rod. Each bracket 62 is formed with a horizontal slot 64 that opens out of the front of the bracket and receives the torsion rod 54 in sliding engagement therewith. The free extremity 63 of the adjusting lever arm 56 depends through a slot 66 formed in a block 68 secured to the face of the standard 14 below the end of the torsion rod 54. An adjusting screw 70 is received in a threaded hole formed in the block. The screw 70 is aligned with the slot 66 in the block and therefore the free extremity 63 so that the inserted end of the screw may be brought into contact with the free extremity 63.

In operation, when the liftin lever is in the lowered position with the cam face 51 out of engagement with the undersurface of the ear 42 a downward pressure is exerted by the torsion rod 54 on the presser bar 22 through the intermediacy of the lever arm 58 and the Ushaped connecting bracket 32. The torque or force applied by the torsion rod 54 is developed by moving the adjusting lever arm 56, integrally connected to the standard end of the torsion rod, in a clockwise direction (as viewed looking from the head toward the standard). Such movement tends to rotate or twist the torsion rod 54 about its longitudinal axis because the connecting lever arm 58, integrally connected to the other end of the torsion rod 54, opposes the rotation of the torsion rod by means of the abutment of the finger 60 with the top surface of the lower leg 36 of the U-shaped bracket 32. By rotating the adjusting screw 70 so that the lever engaging end moves inwardly toward the standard 14 the screw end pushes the extremity 63 of the lever 56 toward the standard thereby increasingly to twist the torsion rod 54 thus to increase the torque which in turn increases the downward pressure on the presser bar 22. Thus, by rotating the screw the force with which the presser foot 24 will be biased downwardly may be regulated' The screw 70 could of course be calibrated to provide the operator with a ready reference for gauging the amount of downward force applied by the presser foot.

It is noted that the torsion rod 54 may be conveniently located relatively to the bracket arm out of the way of other mechanism required to be located in the bracket arm. Furthermore the entire torsion rod 54 and the lever arms at either end may conveniently be located within the confines of the sewing machine.

Having thus set forth the nature of this invention, what I claim herein is:

1. In a sewing machine, a frame including a work supporting bed, a presser mechanism mounted on said frame, said presser mechanism including a presser foot supported above said bed, means for applying pressure to said presser mechanism to urge said presser foot toward said bed, said means for applying pressure to said presser mechanism including a rod having a lengthwise axis, said rod supported by said frame for twisting about said lengthwise axis, means for producing a torque in said rod effectively twisting said rod about said lengthwise axis, and means for applying the torque produced in said rod to urge said presser foot toward said bed.

2. In a sewing machine as set forth in claim 1 wherein said means for producing a torque in said rod includes an adjusting lever connected to said rod at an angle to said lengthwise axis, and means for moving said adjusting lever to apply a force to said rod that tends to twist said rod about its lengthwise axis.

3. In a sewing machine as set forth in claim 2 wherein said means for producing a torque in said rod includes an adjusting lever arm extending at substantially right angles from said rod, and an adjusting member shiftably supported in said frame in contact with said adjusting lever arm and adapted for manual operation to vary the torque applied to the rod.

4. In a sewing machine as set forth in claim 2 wherein said means for applying the torque produced in said rod to urge said presser foot toward said feed dog includes a connecting lever arm extending from said rod at an angle to said lengthwise axis and connected to said presser foot.

5. In a sewing machine as set forth in claim 4 wherein said bearing means for said rod on said frame includes a bracket secured to said frame, said bracket having formed therein a rod accommodating slot, said slot being formed to limit movement of said rod transversely of its longitudinal axis.

6. In a sewing machine as set forth in claim 5 wherein an intermediate bracket is secured to said presser mechanism and said connecting lever arm is in operative engagement with said intermediate bracket, said connecting lever arm extending from said rod closely adjacent to said bearing means, and manually operated means mounted on said frame for releasing the pressure applied to said presser foot by said connecting lever arm.

References Cited UNITED STATES PATENTS 1,758,349 5/1930 Berger et a1 1l2238 2,401,216 5/1946 Becker ll2238 3,329,115 7/1967 Ciecior 112235 PATRICK D. LAWSON, Primary Examiner 

